Powder press with proportional pressing control



POWDER PRESS WITH PROPORTIONAL PRESSURE CONTROL Filed March 21, 1957 R.G. FRANK April 28, 1959 4 Sheets-Sheet 1 M M H m M pmv 3 w .n M A 2 w ml o 3 2 & 1 w 3 87' al 2 5 HP E M n w 0 4 8 m -W. 2 m 3 w w A .llllil 7A S 1 T V/A 7 5 FIG.2a

Raymond G. Frank Mia/Miami April 28, 1959 R. G. FRANK POWDER PRESS WITHPROPORTIQNAL PRESSURE CONTROL Filed March 21, 1957 4 Sheets-Sheet 2 M ama v md n O m y FIG.3'

mhiiiiii- W! iiill m M Q ATTORNEYS mymmm April 28, 1959 R. G. FRANK883,703

v POWDER PRESS WITH PROPORTIONAL PRESSURE CONTROL Filed March 21, 1957 4I 4 Sheets-Sheet s INVENTOR Raymond G. Fronk ATTORNEY S R. G. FRANK Aril 28, 1959 POWDER PRESS WITH PROPORTIONAL PRESSURE CONTROL Filed March21, 1957 4 Sheets-Sheet 4 INVENTOR Raymond G.Fronk ATTO EYS UnitedStates Patent O POWDER PRESS WITH PROPORTIONAL PRESSING CONTROL RaymondG. Frank, Ambler, Pa., assignor to F. J. Stokes Corporation,Philadelphia, Pa., a corporation of Pennsylvania Application March 21,1957, Serial No. 647,639

Claims. (Cl. 18--16.7)

A method for compressing particulate materials to form stepped articlesis described in copending application of Raymond G. Frank, seriallynumbered 647,604 and filed March 21, 1957. In the method of theaforenoted copending application, which is conveniently known asproportional pressing, the problem of powder transfer from one column toanother in front of the multiple punches advancing adjacent to eachother in the die is solved by advancing the multiple adjacent punches tocompact the powder charge from a position prior to compaction of thepowder charge at which the depths of fill in front of the punches are inproportion to the correspondin'g thicknesses of the article to bemolded. Proportional pressing also contemplates that the multipleadjacent punches will be advanced'in the die to compact the powdercharge from such initial fill position at rates which are designed tomaintain constant the proportionate depths of fill initiallyestablished, at least until the molding material ceases to be fluent,which in the usual case will occur at about 10' or 15% of the totalforce which is applied in forming the finished article.

While it will be readily apparent that cam and hydraulic presses havingindependent multiple adjacent upper .orjlower punches, or both, can beset up to accomplish proportional pressing, if the cam profiles areappropriately cut or if the areas of the hydraulic cylinders are in the1 areas will be changed. Retooling in changing from one set-up toanother thus may require the expense'of n'e'w cams or hydrauliccylinders in order to achieve proportional pressing. This is notordinarily feasible.

It is aprincipal -object of my present invention to provide a press foraccomplishing proportional pressing with a variety' of fill ratios andpunch areas as may be ordinarily met in 'theanticipated use of themachine, and in which replacement of cams or hydraulic cylinders will beunnecessary.

This and other objects and advantages of my invention, i

which will become apparent hereinafter, are essentially derived from mydiscovery that proportional pressing can be achieved by controllingindividual punch motions to hold instantaneous unit molding pressuresconstant.

One mechanism for accomplishing proportional pressing utilizing mypresent discovery is based on locating hydraulic cylinders in-themechanical linkages connecting each of the multiple adjacent punches totheir respective drive units and by providing a hydraulic system forcontrolling theflow of hydraulic fluid from and to each ice cylinder tomaintain fixed ratios of hydraulic pressures between the cylinders,proportionate to the ratios of the compression areas of the punchescontrolled by the respective cylinders and to the ratios of themechanical advantages of the cylinders in controlling the punches. Ifthe hydraulic control cylinders are arranged in the mechanical linkagesdriving the punches and for every punch there is at least one cylinderwhich is capable of controlling the force transmitted to the punch,either directly or by difference, the total force applied by the punchescan be controlled such that each punch trans mits a force to the compactwhich will compress'the compact with the same instantaneous unit moldingpressure as each other punch, and the punches will move duringcompression at rates compacting their respective powder columns with auniform increase. in density thereby assuring that no transfer ofmolding powder will occur from the column in front of one punch to thecolumn in front of another. v

I have found that this movement of the punches corresponds substantiallyto the movement described above as proportional pressing and the ratiosof decrease in depth of fill in front of multiple adjacent punches willbe held constant provided, of course, that the depthof fill in front ofeach punch before compaction occurs is inthe same proportion to thedepth of fill in front'of each other punch as are the correspondingdimensions of the final article to be formed.

It should be noted that i-n a hydraulic press, the control cylinders canbe the hydraulic cylinders driving the punches. p

Two embodiments' 'of"my invention are illustrated in the accompanyingdrawings in which:

Figure 1 is a diagrammatic view in vertical section showing therelationship of the principal elements of a press embodying the presentinvention;

' Figures 2a to 2c, inclusive, illustrate the various stages in theoperation of the punches;'

.Figure 3 is a front view of a cam operated press embodying the presentinvention;

Figure 4 is a side view of Figure 3;

Figure 5 is a diagrammatic illustration of the cam operated press ofFigures 3 and 4; and

Figure 6 is a diagrammatic view of an adjustable control device foradapting the presses shown in the preceding figures to form articles ofdifferent dimensions.

Referring to Figure 1, a base structure or block 11 has mounted thereina hydraulic pressure cylinder 12 having a connection to a source ofsuitable hydraulic fluid (not shown). Cylinder 12 and other hydraulicpressure cylinders hereinafter mentioned are fluid pressure motors whichare well known as comprising'recip' rocable. pistons having exteriorlyextending piston rods. Block. 11 is substantially rectangular and hasthreaded bosses .in the corners thereof in which are vertically mountedtie rods 13 extending upwardly from the block 11 and defining a mainpress frame.

The corner rods 13 have mounted thereon a vertically re'ciprocablepressure plate 14 which is limited in its downward movement by collars15 which are aflixed to corner rods 13 beneath plate 14. Centrallymounted on plate 14 are upper and lower hydraulic pressure cylinders 16and 17, respectively.

A centrally apertured pressure plate 18 is mounted on the corner framerods 13 above pressure plate 14. Rigidly interconnecting pressure plates14 and 18 are push, rods 19 which are connected at their ends to thepressure plates by means of collars 20. Thus, pressure plates 14 and 18are maintained in positively fixed relation to each other by rods 19 andreciprocate vertically as a unit. Suitable stops (not shown) areprovided in a conventional manner to limit vertical movement of pressureplates 14 and 18 for fill, compression and ejection functions.

A die table 21 is mounted above plate 18 fixed in position on cornerrods 13 by locking collars 22. Table 21 has a central vertical boreformed with a plurality of rabbets near its upper end to receive die 23into which the punches enter in compacting the article and to receive aclamp ring 23a for securing the die in position.

A pressure plate 24 is mounted above die table 21 on the frame rods 13for vertical, reciprocating movement to bring an upper punch into andout of the die 23 in the table 21. Movement of the plate 24 is guided bythe rods 13 and is produced by motor means in the form of a fluidpressure cylinder 25 similar to cylinders 12, 16, and 17. Suitable stops(not shown) are fastened on rods 13 to limit movement in bothdirect-ions of plate 24 and hence the upper punch. Pressure cylinder 25is mounted in a head plate 26 in which the upper ends of corner rods 13are aflixed and completes the frame of the press. The cylinder 25 isprovided with a piston having a depending rod afiixed at its lower endin a socket in the plate 24. Plate 24 is formed with a depending upperpunch generally designated 30.

A frame (not shown) is mounted on a base to one side of the pressstructure described above and for-ms supporting and enclosing means forpumps and their drives, for pipes connecting such pumps with cylinders12 and 25, and for control valves by which distribution of pressure tosuch cylinders is controlled. Upper hydraulic pressure cylinder 16mounted on pressure plate 14 has an upwardly extending piston rod onwhich is mounted an inner punch holder 27 which has a vertical slot 28formed therein toward its lower end. Stops (not shown) are fastened topunch holder 27 to limit its upward movement by engagement of the stopswith plate 24 and die table 21. Stops (not shown) are fastened to thepiston rod of cylinder 16 to limit downward movement of punch holder 27.A core rod holder which includes a supporting bar 29 is mounted in slot28. Supporting bar 29 passes through slot 28 and is supported at itsouter ends by rods (not shown) having their upper ends secured to table21. A core rod 31 passes through inner punch holder 27 along thevertical axis of the press and its lower end threadedly engagessupporting bar 29. The upper end of inner punch holder 27 is providedwith an upwardly extending inner punch generally designated 32. Innerpunch holder 27 passes through the centrally located vertical bore inpressure plate 18 which forms a guide for punch holder 27 An upwardlyextending outer punch generally desig nated 33 is coaxially mountedabout inner punch 32 and is attached at its lower end to the upper sideof pressure plate 18.

The upwardly extending piston rod of hydraulic pressure cylinder 12within block 11 and the depending piston rod of lower reciprocablehydraulic pressure cylinder '17, mounted on the underside of pressureplate 14 are connected by suitable means such as threaded collar 35.

Within base block 11 hydraulic pressure proportionating cylinders 36 and37 are mounted in side by side relation. The pistons of cylinders 36 and37 are connected to a lever 38 which pivots about a fulcrum shaft 39mounted on block 11. Pressure cylinder 16 and proportionating cylinder36 are interconnected by conduit 40. Pressure cylinder 17 andproportionating cylinder 37 are also interconnected by a similar conduit41.

Operation of the press shown in Figure 1 will be explained inconjunction with Figures 2a to 2c.

The hydraulic fluid supply to cylinders 12 and 25 is connected to causesuch cylinders to withdraw their associated punches from die table 21such that punch 30 is raised clear of table 21 while punches 32 and 33are positioned as shown in Figure 2a. With the punches so positioned acharge of powder molding material, such as powder brass, is deliveredinto the center of die 23. Fluid is then connected to cylinder 25 toadvance punch 36) into die 23 to the position shown in Figure 2b. Thismovement is stopped prior to compaction of the charge of moldingmaterial just at the point at which pressure will begin to build up. Thestops limiting lower punch downward movement are set such that therelative separation of punch 33 from punch 30, when the latter is at theinitial compacting position of Figure 2b, is in the same proportion tothe relative separation of punch 32 from punch 30 as these measurementsbear to each other in the ultimate positions the punches achieve inmolding the desired article.

Full fluid pressure is then applied to cylinder 12 to drive punches 32and 33 into the die against the molding material. The stops are, ofcourse, positioned to limit sliding movements of the punches into die 23at the desired ultimate position shown in Figure 20. As the punchesapproach this position, however, they do so such that adjacent punches33 and 32 arrive at their ultimate positions of advance substantiallysimultaneously and at a substantially constant speed ratio, whileexerting throughout their respective strokes substantially equalinstantaneous unit molding pressures at any given instant. The powdercolumns above punches 32 and 33 are thus uniformly compacted to producean annular stepped article of substantially uniform density. This resultis achieved in the following manner.

As fluid pressure is applied to cylinder 12, its associated piston isdriven up, thus driving the piston of cylinder 17 upwardly in cylinder17. The latter movement increases the pressure on the fluid confined incylinder 17 and hence increases the force applied to platen 14 tendingto advance punch 33 into die 23. The same increase in fluid pressurealso displaces fluid from cylinder 17 into proportionating cylinder 37causing its associated piston to extend upwardly and rotate lever 38 todrive the piston associated with proportionating cylinder 36 down intosuch cylinder. The pressure of the fluid in cylinder 36 is thusincreased and fluid is displaced from it into cylinder 16 to drive itsassociated piston, and punch, 32, upwardly. Fluid pressure is, ofcourse, applied simultaneously to cylinder 25 and cylinder 17, such thatall punches reach final compression together.

It is readily apparent that if the fulcrum 39 of lever 38 is adjustedhorizontally to take into account the ratio of areas on the upper facesof punches 32 and 33, cylinders 36 and 37 function to move punches 32and 33 relative to each other as pressure is increased to cause the unitmolding pressure exerted by each punch to equal that exerted by theother. Thus, as the punches advance into the die to compact theirrespective powder columns, they do so with strokes proportionate to thedepth of fill of their respective powder columns at initial compaction(Figure 2b). The punches thus arrive simultaneously at the desired finalpositions shown in Figure 20.

Although a single outer punch and a single inner punch are illustratedin Figures '1 and 2, any number of punches coaxial and otherwise, can beemployed by providing a plurality of cylinders similar to cylinder 16,which cylinders are in similarly proportionated fluid pressurecommunication with cylinder 17.

This invention can also advantageously be incorporated in cam typepresses as is illustrated in Figures 3, 4 and 5 wherein like elements tothose of Figures 1 and 2a, b and c are provided with the same numbers.Referring to the drawings, the press illustrated comprises a main frame51 provided with a die table 52 which supports a die 23 having a smoothvertical bore in which the molded article is to be formed. For theformation of a flanged article, such as shown in Figure 2c, the press isprovided with a core rod 31 lower inner and outer concentric punches 32and 33, respectively, and upper punch 30. The die, punches and core rodare similar to those illustrated in Figures 1 and 2a to 20, inclusive.

Upper punch 30 is carried by a slide 53 mounted for verticalreciproation between parallel guides 53a and 53b carried by frame 51.Slide 53,is reciprocated by means of a lever 54 mounted to frame .51 at54a and having the forward end thereof entering between adjustableabutments 53c'and 53d carried by slide 53. These abutments may be formedof disc elements provided with v slide mounted between two guidesprovided on the lower front portion of frame 51. The slide is formed oftwo side members 61a and 61b joined at the top by a yoke piece 61!:which carries the punch 33, and also joined at' the lower ends by abridging portion 61d'shown in the dotted lines in Figure 4. This slideis reciprocated on the compression stroke by means of'a lever 62 pivotedto frame 51 at 62 and having two arms 62a: and 62b extending forwardlyfrom the pivot point and positioned under adjustable abutments 61a and61b carried by slide Parts 610: and 61b. r l

Mounted between slide parts 61a and 61b is a third slide 63 whichcarries inner tubular punch 32. Mounted the lowerportion of slide 63is ahydraulic pressure cylinder 632, the piston rod {off-which cylinderextends ,vertically downward from slide 63and'is provided at itsexterior' end with'an adjustable abutment 63a." Slide 63 is movedvertically on the compression stroke by means of a third arm 62c onlever 62 which engages the adjustable abutment 6312 on the lower end ofthe piston rod of cylinder 63e. The rear end of lever 62 is connectedthrough a hydraulic pressure cylinder 64 to a second lever 65 pivoted toframe 51 at 651m and carrying a cam follower 65b which engages anoperating cam diagrammatically represented by the circle 650 in Figure4.

A fourth cam operated lever 66 (the ejection lever) is pivotallysupported on the frame 51 at 65a and is provided with three forwardlyextending arms, two of which, 66a and 66b, enter openings formed inslide parts 61a and 61b and engage adjustable abutrnents 61m" and 61b"carried by these parts. A third forwardly extending arm 66c on lever 66enters the opening in slide 63 and engages an adjustable abutment 63bcarried by this slide. The rear end of lever 66 is provided with a camfollower 66d which engages an operating cam represented by the circle662, Figure 4. The ejection mechanism is substantially that disclosed inUS, Patent 2,499,980, and since it forms no part of this invention willnot be further discussed.

The core-rod 31 mounted within punch 32 extends downwardly through theupper end of slide 63 and into an opening formed Within this slide asshown in Figure 3. The lower end of the core-rod is supported in fixedrelation with die 23. It can, of course, be mounted for verticalreciprocation by means of a suitable cam-operated lever, if desired.

Referring more particularly to Figure 5, cylinders 63e and 64 areprovided with means for proportionate transfer of hydraulic fluidtherebetween as, for example, through trunnion mounted hydraulicpressure proportionating cylinders 70 and 71 which operate insubstantially the same manner as the proportionating cylinders 36 and 37illustrated in Figure 1 and described above. Cylinder 64 is connected tocylinder 70 by a suitable conduit 72 for transfer of hydraulic fluidbetween the cylinders, and cylinders 63e and 71 are connected in likemanner by conduit 73. The pistons of proportionating cylinders 70 and 71are connected by their respective piston rods to a bell crank 74.

Operation of the press is as follows: compression form articles havingdijferent structural configurations force is applied tovreciprocablecylinder 64.by rotation of cam 65c causing cylinder 64 to movevertically downward. Movement of cylinder 64 is transferred to lever 62through the piston of cylinder 64, which movement is transferreddirectly to outer punch 33 carried by yoke 610 on slide parts 61a and61b through arms 62a and 62b and indirectly to inner punch 32v throughcylinder 63e in slide 63 by arm 62c. The total force acting on thepiston of cylinder 64 is equal to the sum of the forces acting on thepunches by the respective partly compressed powder columns times theratio of the length of arms 62a, 62b and 620 measured from pivot 62' tosubstantially their ends to the length of lever 62 measured from pivot62' to its connection with the piston of cylinder 64. The ratio of thelength of the arms of bell crank lever 74 is selected with regard to themechanical advantage of cylinder 64 over cylinder 63b such that theforce acting on the piston of cylinder 63e and, hence, punch 32, will bein the same proportion to the force acting on punch 33 as are thecross-sectional areas of the punches to each other.

It is thus evident that the press in Figures 3-5 also functions inexactly the manner described with respect to Figures 2a-2c for the pressshown in Figure 1 to achieve proportional pressing in which punches 32and 33 are advanced into the die with stroke lengths proportional to theconfiguration of the desired article while at all times exerting equalinstantaneous unit molding pressures. I

It is evident that conversion of a particular press to can beaccomplished by changing the punches where required, by resetting thestops and by repositioning the fulcrum 39 of lever 38 or the fulcrum ofbellcrank lever 74. A lever having an adjustable fulcrum is desirable inmany instances to accomplish the last. Figure 6 shows such a lever inwhich the reference numbers and 81 represent proportionating cylinders,such as those illustrated in Figure 1 and designated by the referencenumbers 36 and 37 and those designated by the numbers 70 and 71 inFigure 5.

In the device shown in Figure 6 piston rods 82 and 83, respectivelycarried by pistons 84 and 85 located respectively in cylinders 80 and81, are pivotally engaged at their outer ends with a lever 86.Intermediate at its ends lever 86 is pivotally mounted receiving a pin87 supported on a base 88. Base 88 is suitably mounted for horizontalsliding movement in a frame 89, which can form a portion of the base ofthe press or which can be positioned entirely apart from the press.Within frame 89 there is located a worm drive 90 which meshes with a cog91 affixed to base 88 of fulcrum pin 87. The pivotal connection ofpiston rod 82 and of piston rod 83 to the opposite ends of lever 86includes respectively pins 92 and 93 afiixed on the ends of rods 82 and83 and which are slidably received in elongated slots 94 and 95 locatedin the ends of lever 86. Thus when it is desired to change theproportionate forces driving punches 32 and 33 in order to accommodatediiferent relative stroke lengths of the punches, or different relativepunch areas, rotation of worm 90 can be employed to shift the fulcrumpoint of lever 86 against which the proportionating cylinders 80 and 81operate.

While the preceding specific description has been confined to theemployment of control hydraulic cylinders and of proportionatingcylinders to balance the forces applied by the punches by the controlcylinders to maintain the unit molding pressures exerted by each punchidentical, it will be evident, particularly in the case of largertonnage presses where hydraulic control pressures would be high, thatthe same results can be achieved and proportional pressing accomplishedif the press is provided with a device which will sense the unit moldingpressure exerted by each punch at any instant (a linear function of theforce applied to the punch) and a device for controlling application offorce to each punch which is operably responsive to the sensing devicesto correct any deviation in unit molding pressures exerted by thevarious punches and thus hold the unit molding pressures exerted by eachpunch at the same value at any given instant.

I claim:

1. A proportional pressing control device for a molding press havingmultiple adjacent punches which includes means sensitive to the unitmolding pressure exerted by each said adjacent punch, and drive meansfor each said adjacent punch including means controlling the movement ofeach said punch operably responsive to the associated pressure sensitivemeans to maintain the unit molding pressure instantaneously exerted byeach said punch substantially equal to the unit molding pressure exertedby each other said punch.

2. A proportional pressing control device for a molding press havingmultiple adjacent punches which includes means operably connected toreciprocate each said punch, including a separate hydraulic pressuremotor positioned to transmit force to each said punch, and hydraulicfluid transfer means communicating with each of said motor sensitive tothe hydraulic pressure developed therein and operable to transferhydraulic fluid to and from each said motor to maintain the hydraulicpressure in each said motor in a predetermined constant proportion tothe hydraulic pressure in each other said motor.

3. A proportional pressing control device for a molding press having afirst punch and a second punch, said punches being reciprocable adjacenteach other, which includes means for reciprocating ,saidpunchesincluding a first hydraulic cylinder positioned to transmit force tosaid vfirst punch and a second hydraulic cylinder positioned to transmitforce to said second punch, and hydraulic fluid transfer meanscommunicating with each said cylinder sensitive to the hydraulicpressure therein operable to transfer hydraulic fluid from and to saidfirst cylinder and to and from said second cylinder to maintain thehydraulic pressure in said first cylinder in a predetermined constantproportion to the hydraulic pressure in said second cylinder, wherebysaid punches exert substantially equal instantaneous unit moldingpressures.

4. A control device according to claim 3 in which said second cylinderis positioned to transmit force to said first punch in series with saidfirst cylinder.

5. A control device according to claim 3 in which-said hydraulic fluidtransfer means comprises a third hydraulic cylinder in opencommunication with said first cylinder, a fourth hydraulic cylinder in:open communication with said second cylinder, and pivoted lever meansmechanically linking said third and fourth cylinders to react againsteach other about a fulcrum.

References Cited in the file .of this patent UNITED STATES PATENTS2,556,951 Weidner June 12, 1951 FOREIGN PATENTS 497,996 Canada Dec. 1,1953

